As a system for transferring data to be provided by a data provider to a user, there are a system in which a provider provides data for a user's device through a public telephone line, depending on the user's access, (e.g., networks using, for example, a personal computer), and data broadcasting systems that send data information by multiplexing it into a normal program in a television broadcasting.
In a data broadcasting for television broadcasting, there has been proposed a system in which, from a broadcasting station, hyper media data equivalent to data provided by a computer network is multiplexed into a broadcasting data and then sent it, so that a user obtains information equivalent to that obtained by a connection to a wide computer network, by receiving broadcast waves via a television receiver.
Although a sending via a broadcasting is performed by high-speed and at low cost, it is not performed according to an individual user's demand, and it is impossible to send all of a large amount of data acquired across the entire computer network.
On the other hand, data access by a network connection has a problem that its communication cost is high.
As a prior art broadcast providing system, Japanese Patent Published Application No. 8-32534(1996) discloses a system with which a given data is efficiently provided for a user at low cost. Specifically, data provided by a plurality of data (information) providers are concentrated on a service providing center, in which then, from several information transfer networks, one is selected depending on the type of a data to be provided. In cases where a large amount of data (information) is provided for a user, and data is provided for an unspecified user, data is sent via a high-speed information transfer network (e.g., information transfer networks utilizing a broadcasting satellite or a communication satellite, ground waves, CATVs). In cases where a relatively small amount of data is provided, and data is provided for a specified user, data is sent via a low-speed information transfer network (e.g., a public communication line, such as a public telephone line).
In this system, since a certain data is sent via a high- or low-speed information transfer network according to its data type, a user can obtain a specified data via one of plural information transfer networks. However, it is impossible to know the origin of data that is information from a computer network line and provided via a broadcasting, and to know the origin of data that is provided from information via a broadcasting, through a computer network line. Therefore, this system is inconvenient for obtaining a desired data.
Further, this publication has no description as to whether an identical data can be obtained under a different condition, i.e., from both high- and low-speed information transfer networks. Presently, there exists no data receiving apparatus for receiving data efficiently when providing an identical data via both a computer network line and a television broadcasting.
Meanwhile, broadcasting contents of a television or a radio are captured as a program, and are constructed according to channel and time. Additional information for describing content and construction of a program is also constructed by a table according to channel and time, although a genre code appending and a grouping of programs having an identical category have been proposed (see Practice MPEG Text by Point Picture Style, supervised by Hiroshi Fujiwara, issued by Kabushikikaisha Asuki).
Examples of data broadcasting that broadcast a data program by multiplexing it into a normal television program, includes one in which a data to be broadcasted is systematically arranged; a common header is appended to related plural data; and a common host header is appended to plural headers for preparing a hierarchical structure, whereby information of the hierarchical structure is broadcasted together with the data.
Since a prior art broadcasting method in which additional information related to programs is sent by multiplexing it to the program, is directed to send additional information whose main content is a program order according to time, such information is effective for selecting a normal television program. However, if a desired program is a data program, referential and hierarchical relationships between programs are unknown, making it impossible for a user to efficiently perform a retrieval and a selective acquisition of a data program.
In a prior art teletext, information of a hierarchical structure is broadcasted by appending an index to each data, and then appending a common index to plural indexes. For example, Japanese Patent Published Application No. 8-22471 (1996) discloses to append an index to an image data and then append a common index to plural indexes, whereby a hierarchical structure is prepared for data whose final data is an image, and information of the hierarchical structure is then broadcasted together with the data. Such a data broadcasting method enables a user to readily obtain necessary information by tracing a hierarchical structure, depending on a header.
In this prior art data broadcasting method, an index is appended to a data itself and a hierarchical structure is represented using the index, on the assumption that an identical information is repeatedly sent in a given short cycle through a given channel. For recognizing the entire hierarchical structure on a receiver end, it is necessary to receive all the final data. Thus, a final data size should be limited, and this method is unsuitable to a data broadcasting in which a final data is sent across plural channels for a long irregular cycle.